The invention relates to the manufacture of corrosion resistant steel components, and in particular to such components which have an aesthetically pleasing uniform dense black finish.
It is known from eg. U.S. 4,496,401 to form a corrosion resistant epsilon iron nitride or carbonitride layer on an alloy steel component. According to GB-A-2180264 the treated layer is given a mechanical surface finish, followed by a gaseous oxidation to provide an oxide-rich surface layer.
The invention is based on the realisation that if a component having a selected surface layer is subjected to predetermined gaseous oxidation followed by a predetermined surface preparation treatment the component is provided with both corrosion resistance and an aesthetically pleasing black appearance. Further, such a component may be used without the need for a further coating e.g. a wax sealant or paint or a film of oil.